The invention disclosed herein relates generally to the processing of mail, and more particularly to a method and system to detect possible contaminants in the form of loose particulate matter contained within a mail piece.
The United States accounts for the largest domestic letter traffic in the world, handling almost 200 billion pieces of mail each year. The United States Postal Service (USPS) employs more than 850,000 employees and operates more than 44,000 post offices throughout the country. In many respects, the economy of the country is dependent upon the postal system being able to efficiently and quickly deliver mail pieces. Any type of major disruption in the delivery of mail could have potentially serious detrimental effects on the country as a whole.
Recently, attempts have been made to disrupt the postal system and use it as a weapon of terror and fear by the inclusion of harmful chemical or biological contaminants, such as, for example, the spore-forming bacterium Bacillus anthracis (anthrax), within or on a mail piece. Such contaminants can be carried in several forms, including for example, a powder form. The harmful effects of only a few contaminated mail pieces can be far reaching, as cross-contamination of other mail pieces can easily occur when the mail pieces come in contact with each other or are passed through the same machines during sorting. The Centers for Disease Control and Prevention estimates that tens of thousands of mail pieces could have become cross-contaminated from only two contaminated mail pieces. The use of the postal system for such purposes has resulted in the need for a reliable way to detect small amounts of loose and possibly dangerous particulate matter contained within a mail piece before they are processed by the postal authority or opened by the recipient.
Ideally, it would be desirous for the postal authority to examine and/or test each piece of mail individually for any possible contaminants before it enters the mail system, thereby isolating any contaminated mail pieces and preventing any cross-contamination. Such examination could be performed, for example, by visually inspecting each mail piece for a powdery substance contained therein. With the large volume of mail processed daily, however, the cost and time associated with visually inspecting each piece of mail makes such inspection unfeasible. It is imperative that any such testing and/or examination be capable of being performed both cost effectively and quickly to avoid delays in processing and delivering the mail.
Thus, there exists a need for a reliable way to quickly and cost effectively detect small amounts of loose and possibly dangerous particulate matter contained within a mail piece.
The present invention alleviates the problems associated with the prior art and provides a method and system that can quickly and cost effectively detect small amounts of loose particulate matter contained within a mail piece.
In accordance with the present invention, the mass of each mail piece is determined two times utilizing a vibrating tray scale. During the first mass determination, pressure is applied to the entire surface of the mail piece to secure it to the scale tray, thereby including the mass of everything contained within the mail piece, including any type of loose particulate matter. During the second determination, pressure is applied to only a plurality of discrete individual pressure points on the mail piece to secure it to the scale tray, thereby allowing any loose particulate matter contained within the mail piece to still move freely within the mail piece. Accordingly, the mass of any such loose particulate matter will not be included in the total mass of the mail piece as determined by the vibrating tray scale during this measurement.
If the mail piece contains any type of loose particulate matter, there will be a difference in the mass of the mail piece when the entire envelope is secured to the scale tray and the mass of the mail piece when only portions of the mail piece are secured to the scale tray as determined by the vibrating tray scale. The mail piece can then be diverted from the normal processing path for further inspection, thereby preventing cross-contamination of other mail pieces and processing equipment.